Father Sullivan taught the Classics at Clongowes – that is, Greek and Latin. He was not the best of teachers: his manner was too humble for him to effectively ensure discipline over the class, while at the same time, he was the kind of teacher that loves his subject so much that he would get carried away in his teaching, leaving the class behind.
Although he lacked the talent for teaching in the classroom, many of his pupils remember practical and valuable advice given to them by Father. One boy, who afterwards had a successful career as a lawyer, recalled how Father Sullivan once said to him: “As soon as you get qualified, write a learned book.” “On what?”, replied the surprised boy. “On anything”, said Father decidedly. In fact, the pupil afterwards wrote a very successful legal textbook.
Father Sullivan acted as Spiritual Father to his boys during nearly all his years at Clongowes. His boys regarded him with great veneration – he struck a cord in their hearts when they saw the familiar figure, with the head bent over in prayer, the threadbare garments along with the low hurried voice when it spoke of God. At the time of Father’s death, one boy wrote to his mother: “Father Sullivan (we call him the Saint, Mum) is dying, you will be sorry to hear. By the time this letter arrives, he will probably be in heaven.”
Captain Sidney B. Minch of Mageney, Co. Kildare (captain of Clongowes in 1911-2), recalled of Father John Sullivan:
“I found Father John at his best on walks during that same last year. (…) How he talked! He found out what you were interested in, and then brought God or some saint right into the middle of it so naturally that even our young minds became aware of his constant preoccupation with the things of God. (…) He was fascinated by the heroism of great saints, particularly those who had saved themselves from a life of terrible indulgence. How often do I remember him referring to St. Augustine and St. Mary Magdalen.”
Rev. Roland Burke-Savage, S.J. writes:
“Father Sullivan had a noticeably great devotion to the Stations of the Cross – quite often if one dropped into the Boys’ Chapel during recreation one would find him alone in obviously fervent prayer before the Stations.”
Despite the long hours which Father spent in prayer, along with his constant visits to the suffering and the poor, he still managed to play his part fully in the life of the Community. During his first few years as teacher, Father used to accompany the boys on their usual holiday in the summer, and he would throw himself full-heartedly into any excursions or activities. The same Jesuit recalls an incident which shows Father Sullivan’s goodness of heart and fraternal charity: on a holiday in Donegal, a young pupil had mapped out a trip around the beauty spots of the surroundings. The only difficulty was that the boy and his companion would have to get Mass at 2.30 a.m. in order to catch the early ferry. Father Sullivan cheerfully agreed to rise and say Mass at the required time, and then helped the party prepare for the journey.
Father James Tonkin, S.J., writes how he was once talking to a nun who had filled many posts – Reverend Mother and Higher Superior in Ireland – and had sound judgement. When he mentioned Father Sullivan, the nun said of him very emphatically, “A man dead to self.”
When conversing with his fellow-religious, they were greatly edified at his meekness, humility and charity. Father would often offer to do the most menial tasks, the heaviest work and the latest Mass, notwithstanding that he had a tiring week of daily duties.